The present invention relates to catheters for diagnosis of, or delivery of localized therapy to, a target region of a body lumen, and, in particular, to balloon structures for positioning a catheter or similar device within the heart.
Catheterization is a type of procedure performed for a variety of purposes, including diagnostic, interventional, and other therapeutic procedures. In catheterization techniques, a long tubular catheter is introduced into the body through a puncture site. It is then passed to a target site, usually through the circulatory system. The therapeutic procedures are usually accomplished at the distal end of the catheter by manipulation of the proximal portion of the catheter remaining outside the body, or by introducing instruments or therapeutic agents into the catheter body at the proximal end for passage through the catheter to the target site.
During many of these procedures, it is necessary to keep the distal end of the catheter in a relatively stable position to perform the desired procedure. In order to ensure that a catheter is maintained in the proper position, it is common to use an expandable balloon disposed near the distal end of the catheter shaft. These catheters typically include a lumen that extends from the proximal end to the balloon end and provide fluid to the balloon for its inflation. Inflation of the balloon causes the balloon to engage the wall of a lumen. The procedure is then performed. Once completed, the fluid is removed from the balloon, thereby deflating the balloon and allowing the catheter to be removed.
Balloon catheters are commonly used to facilitate a number of percutaneous medical treatments such as pressure monitoring, cardiac output and flow monitoring, angioplasty, artificial vaso-occlusion, cardiac support, and cardiac ablation. Such catheters can also deliver therapeutic agents or energy once a target region is identified. Cardiac ablation catheters, for example, delivery energy, which may be in the form of heat, electric current or radiation, in order to eliminate (i.e. xe2x80x9cablatexe2x80x9d) the source of a cardiac arrhythmia. Such catheters typically include an optical apparatus contained within the catheter. The catheter can also include other structures, such as a lumen through which pharmaceutics, biologics, or photoactivatable agents are delivered, as well as mapping electrodes, and/or a sampling system for sampling a tissue or fluid specimen.
Although various types of balloon anchored catheters have been proposed, they often suffer from one or more limitations. A serious drawback to using balloon catheters is that the balloon can cause a total block to the flow of blood through the lumen, depriving tissue of needed blood. This can cause tissue damage, even when the procedure is performed expediently. In addition, blood that is trapped in the occluded area can clot and cause thrombosis.
Consequently, there is a need for better balloon catheter devices that can provide irrigation to reduce the chance of clotting, and/or locally clear blood from a target site without necessarily causing a total blockage of blood flow.
The present invention is directed to a balloon catheter having an irrigation sheath. The structure can include two expandable membranes disposed about a catheter. The first inner membrane is generally or substantially sealed and serves as a balloon to position the device within a lumen. This balloon structure, when filled with fluid, expands and is engaged in direct contact with the tissue. A second (outer) membrane is not completely sealed and instead provides a pathway for delivery of fluid at the treatment site.
In one embodiment, the outer membrane is an irrigation sheath, partially disposed about the occluding inner balloon, and provides irrigation at a treatment site (e.g. so that blood can be cleared from an ablation site). The entire structure can be deflated by applying a vacuum which removes the fluid from the inner balloon. Once fully deflated, the catheter can be easily removed from the body lumen.
In another embodiment of the present invention, the distal end of the sheath, which provides fluid to the treatment site, is position to direct fluid toward the tissue being ablated. In yet another embodiment, the sheath contains fluid releasing pores.
One advantage of the present invention is that irrigation provided by the second membrane reduces hematocrit and the chance of clotting. In phototherapy applications, the removal of blood from the treatment site allows for the unobstructed and uniform delivery of ablative energy. In addition, the irrigating fluid cools the surface of the target site, thereby preventing overheating or burning of the tissue, or coagulation. Moreover, the use of two membranes permits the delivery of two separate fluids, a physiologically compatible fluid and an inflation fluid.